For 10/100 Mbps connectivity, three basic options are available for different PHY. The first option is a “6 core” circuit. This includes 1 common mode choke, 1 isolation transformer, and 1 auto transformer per twisted pair. The second option is a “4 core” circuit. This includes 1 three wire common mode choke and 1 isolation transformer per pair. The third option is another “4 core” circuit that includes 1 two wire common mode choke and 1 isolation transformer per pair. Although each option allows data transmission at 10/100 Mbps, each option will perform differently in regards to EMI.